The invention pertains to the field of art of making construction members which are fabricated of separate components of similar and chemically compatible elements, namely glass fiber and a hardened resin, to produce improved mechanical characteristics, particularly with respect to resisting bending and lateral deflection.
A number of attempts have been made to produce acceptable poles, planks and other construction members of glass fibers impregnated with a hardened resin. U.S. Pat. No. 3,013,584 illustrates a tubular supporting member which was produced in order to employ the advantages of glass fiber materials. While the aformentioned patent illustrates the concept of inner and outer tubular glass fiber portions having a honeycomb interposed therebetween, the construction of prior art devices is not of such a nature as to provide the necessary resistance to bending moments and lateral deflection which is often required in a construction member. For instance, it is highly desirable to use a construction material in the manufacture of electric power transmission systems which is nonconducting, resistant to weathering and corrosive influences, relatively inexpensive, and attractive in appearance. While most lower voltage transmission poles were previously formed of wood, other materials are now being employed in order to overcome the lack of uniformity of wood transmission poles with respect to appearance and resistance to the weather. Furthermore, in that it is the tendency for wood power transmission components to bend under high lateral forces, it is necessary to use multiple components and guy cables with wood transmission components in order to produce the necessary resistance to bending. For instance, electrical utility system cross arm dead-ends conventionally formed of wood are unsightly due to the necessity for using two cross arm members of relatively large cross section to provide sufficient strength characteristics to resist the bending forces imposed thereupon by the electrical transmission lines.
Pole type construction members formed of glass fiber components have not heretofore had sufficient resistance to bending and flexing to permit elongated poles such as would be suitable in the electric transmission system art to be produced. Previous glass fiber construction member arrangements were unable to overcome the inherent tendency of relatively long and slender glass fiber members to bend or "whip".